SMARTY_DIR
Smarty目录

This should be the full system path to the location of the Smarty class files. If this is not defined, then Smarty will attempt to determine the appropriate value automatically. If defined, the path must end with a slash.
定位Smarty类文件的完整系统路径，如果没有定义Smarty目录，Smarty将会试着自动创建合适的值。如果定义了,路径必须要以斜线结束。

// set path to Smarty directory
define("SMARTY_DIR","/usr/local/lib/PHP/Smarty/");

require_once(SMARTY_DIR."Smarty.class.php");